Try thinking through the problem as a switch position problem and not JMRI. You have two switches, one at each end of the throw bar fitted to both turnouts. You will only have a condition where power is fed to the indicator when both turnouts have fully completed their travel.

Let’s call the two turnouts A and B.

You select the crossover and if both points are wired from the same supply then both will start to move. As soon as A throw bar starts to move power to the straight through indicator is cut - we go onto the inconsistent state. ?The same is happening to turnout B. Whichever throwbar completes its travel first will cause the second switch to switch power not to the indicator but to the other turnouts second switch. It is only when the slower turnouts bar is fully across will the circuit to the indicator be made. You must have an indication from both turnouts to form the indication that the crossover is set ready to use. It does not matter which turnout moves first they are both wired the same. Both must be fully over to trigger the indicator.

It’s a wiring problem/solution to a logic problem rather than a JMRI problem because it relies upon the physical position of the turnout and not logic.

Dave